It is well known in the art of golf-club making that the accuracy, trajectory, and distance of a golf shot are influenced by the flex or stiffness of a golf shaft. The bending stiffness of a golf shaft is commonly represented in terms of a frequency, since bending stiffness and vibration frequency are interrelated. Most manufacturers clamp the shaft only at the butt end to measure the vibration frequency. However, vibration frequency measurements, performed in this manner, do not accurately represent the bending stiffness across the entire shaft. Alternatively, the bending stiffness of a golf shaft may be determined by measuring the cantilever displacement of the golf shaft under a known load. These measurements are typically taken only at the butt and tip sections of the shaft, thus providing limited bending stiffness data to the golfer.
Additionally, the torsional stiffness of a golf shaft may be determined by measuring the torsional displacement of the shaft under an applied torque for a given cantilever length. This method generates an overall torsional stiffness value for the shaft, but does not provide the varying localized torsional stiffness values across the shaft. Accordingly, it is difficult to fine tune the torsional stiffness of the shaft to fit the needs of the player.